Ria Misra

What makes a dead star explode? Scientists have long suspected a mechanism for making a white dwarf go supernova, but they weren't able to confirm it — until now.

ESA recently trained its INTEGRAL observatory on an exploding supernova in the M82 galaxy, and were able to catch it in the act as it threw off gamma rays in its final death throes. The signature of those gamma rays, says ESA, are hard evidence of just how fusion is taking place and by what kind of process it happens.

They put together the above sequence of images to explain just how the whole thing unfolds, along with this annotated guide:

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A white dwarf, a star that contain up to 1.4 times the mass of the Sun squeezed into a volume about the same size as the Earth, leeches matter from a companion star (image 1). The Integral measurements suggest that a belt of gas from the companion star builds up around the equator of the white dwarf (image 2). This belt detonates (image 3) and triggers the internal explosion that becomes the supernova (image 4). Material from the explosion expands (image 5) and eventually becomes transparent to gamma rays (image 6).